Control method of phase change water heater, phase change water heater system and readable storage medium

Abstract

The invention discloses a control method of a phase change water heater, a phase change water heater system and a readable storage medium. The control method of the phase change water heater comprises the steps that the current state variable, the boundary condition and the control variable of the phase change water heater are obtained; an optimization target of the phase change water heater is obtained; based on the current state variable, the boundary condition, the control variable and the optimization target, a predictive control model is used for obtaining a control decision of the phase change water heater; and controlling the phase change water heater based on the control decision so as to realize an optimization target. By means of the mode, the control method of the phase change water heater can effectively evaluate the phase change water heater through the predictive control model, and therefore optimization control can be conducted according to the optimization target, and the performance of the phase change water heater is improved.

Description

Technical Field

[0001] This application relates to the field of water heater technology, specifically to a control method for a phase change water heater, a phase change water heater system, and a readable storage medium. Background Technology

[0002] Phase change water heaters use the latent heat of phase change materials to store heat instead of the sensible heat of water. Therefore, compared to traditional water heaters, they are smaller in size and do not require a water tank. Furthermore, the auxiliary heating system of a phase change water heater is an electric heater separate from the phase change heat exchanger, and a mixing valve is provided at the water outlet.

[0003] In existing technologies, the output electrothermal rate of phase change water heaters is adjustable, but the adjustment capability is limited. Furthermore, the control of their auxiliary heating system is rule-based, meaning that the electric heater and water pump are controlled according to pre-defined rules based on real-time measurements of system state variables. This control strategy is relatively simple, failing to maximize the performance of the phase change water heater and thus reducing the user experience. Summary of the Invention

[0004] To address the aforementioned problems, this application proposes a control method for a phase change water heater, a phase change water heater system, and a readable storage medium, aiming to solve the problems described above.

[0005] To solve the above-mentioned technical problems, one technical solution adopted in this application is: to provide a control method for a phase change water heater, the control method comprising: acquiring the current state variables, boundary conditions and control variables of the phase change water heater; acquiring the optimization objective of the phase change water heater; acquiring the control decision of the phase change water heater using a predictive control model based on the current state variables, boundary conditions, control variables and optimization objective; and controlling the phase change water heater based on the control decision to achieve the optimization objective.

[0006] The predictive control model includes a predictive model and an optimization solution model. The steps for obtaining the control decision of the phase change water heater using the predictive control model based on the current state variables, boundary conditions, control variables, and optimization objectives include: inputting the current state variables, boundary conditions, and control variables into the predictive model to obtain the state prediction of the phase change water heater within the prediction window; constructing the objective optimization function and its constraints based on the optimization objectives; and solving the state prediction, objective optimization function, and constraints using the optimization solution model to obtain the control decision of the phase change water heater.

[0007] The optimization objective includes maximizing the hot water output. The steps for constructing the objective optimization function and its constraints based on the optimization objective include: obtaining the first equivalent constraint corresponding to maximizing the hot water output; and constructing the first objective optimization function and its first constraint based on the first equivalent constraint, the physical model of the phase change water heater, the constraints of the state variables, the constraints of the control variables, and the heat release constraint.

[0008] The first equivalent constraint condition includes minimizing the reduction rate of the liquid proportion of the phase change material or maximizing the power consumption of the heater in the phase change water heater.

[0009] The prediction models include a phase change heat exchanger model, a heater model, and a mixing valve model. The phase change heat exchanger model is used to predict the changes in the internal energy of the phase change material and water in the phase change heat exchanger based on the current state variables under the control of boundary conditions and control variables. The heater model is used to predict the changes in the internal energy of the water in the heater based on the current state variables under the control of boundary conditions and control variables. The mixing valve model is used to simulate the mixing valve under the control of boundary conditions and control variables.

[0010] The optimization objective includes maximizing the heat charging efficiency. The steps for constructing the objective optimization function and its constraints based on the optimization objective include: obtaining the second equivalent constraint corresponding to maximizing the heat charging efficiency; and constructing the second objective optimization function and its second constraint based on the second equivalent constraint, the physical model of the phase change water heater, the constraints of the state variables, the constraints of the control variables, and the heat charging constraint.

[0011] Among them, the second equivalent constraint condition includes the largest increase in the liquid proportion of phase change material or the largest power consumption of the heater of phase change water heater.

[0012] The prediction models include a phase change heat exchanger model and a heater model. The phase change heat exchanger model is used to predict the changes in the internal energy of the phase change material and water in the phase change heat exchanger based on the current state variables under the control of boundary conditions and control variables. The heater model is used to predict the changes in the internal energy of the water in the heater based on the current state variables under the control of boundary conditions and control variables.

[0013] The control decision includes multiple sets of time-varying control variables within the prediction window. The steps for controlling the phase change water heater based on the control decision include: in each prediction window of the phase change water heater, obtaining the discrete control variable closest to the current time from the multiple sets of time-varying control variables; and controlling the phase change water heater to operate within the current prediction window based on the discrete control variable.

[0014] To solve the above-mentioned technical problems, another technical solution adopted in this application is: to provide a phase change water heater system, which includes a phase change water heater and a controller, wherein the controller is connected to the phase change water heater and is used to control the phase change water heater based on the control method of the phase change water heater described above.

[0015] The phase change water heater includes a phase change heat exchanger, a first heater, a water pump, and a mixing valve. The inlet of the first heater is connected to the water inlet, the outlet of the first heater is connected to the inlet of the phase change heat exchanger, the outlet of the phase change heat exchanger is connected to the water pump, the water pump is connected to the first end of the mixing valve, and the second and third ends of the mixing valve are connected to the water inlet and the water outlet, respectively.

[0016] The phase change water heater also includes a second heater, the outlet of which is connected to the inlet of the second heater, and the outlet of the second heater is connected to the water pump.

[0017] To solve the above-mentioned technical problems, another technical solution adopted in this application is to provide a readable storage medium that stores program instructions internally, which are executed by a processor to implement any of the above-mentioned control methods for phase change water heaters.

[0018] The beneficial effects of this application are as follows: Unlike existing technologies, the control method for a phase-change water heater in this application includes: acquiring the current state variables, boundary conditions, and control variables of the phase-change water heater; acquiring the optimization objective of the phase-change water heater; obtaining the control decision of the phase-change water heater using a predictive control model based on the current state variables, boundary conditions, control variables, and optimization objective; and controlling the phase-change water heater based on the control decision to achieve the optimization objective. Through the above methods, the control method for a phase-change water heater in this application can effectively evaluate the phase-change water heater using a predictive control model, thereby enabling optimized control based on the optimization objective to improve the performance of the phase-change water heater. Attached Figure Description

[0019] Figure 1 This is a schematic flowchart of an embodiment of the control method for a phase change water heater according to this application;

[0020] Figure 2 yes Figure 1 A flowchart illustrating an embodiment of step S103;

[0021] Figure 3 yes Figure 1 A flowchart illustrating an embodiment of step S104;

[0022] Figure 4 yes Figure 2 A flowchart illustrating step S202 of the first embodiment;

[0023] Figure 5 yes Figure 2 A flowchart illustrating the second embodiment of step S202;

[0024] Figure 6 This is a schematic diagram of the structure of the first embodiment of the phase change water heater system of this application;

[0025] Figure 7 This is a schematic diagram of the structure of the second embodiment of the phase change water heater system of this application;

[0026] Figure 8 This is a schematic diagram of the structure of an embodiment of the readable storage medium of this application. Detailed Implementation

[0027] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0028] Phase change water heaters use the latent heat of phase change materials to store heat instead of the sensible heat of water. Therefore, compared to traditional water heaters, they are smaller in size and do not require a water tank. Furthermore, the auxiliary heating system of a phase change water heater is an electric heater separate from the phase change heat exchanger, and a mixing valve is provided at the water outlet.

[0029] In existing technologies, the output electrothermal rate of phase change water heaters is adjustable, but the adjustment capability is limited. Furthermore, the control of their auxiliary heating system is rule-based, meaning that the electric heater and water pump are controlled according to pre-defined rules based on real-time measurements of system state variables. This control strategy is relatively simple, failing to maximize the performance of the phase change water heater and thus reducing the user experience.

[0030] To address the aforementioned problems, this application first proposes a control method for a phase change water heater. Please refer to [link / reference needed]. Figure 1 , Figure 1 This is a flowchart illustrating an embodiment of the control method for a phase change water heater according to this application, as shown below. Figure 1 As shown, the control method for the phase change water heater in this embodiment specifically includes steps S101 to S104:

[0031] Step S101: Obtain the current state variables, boundary conditions, and control variables of the phase change water heater.

[0032] In this embodiment, it is first necessary to obtain the current state variables, boundary conditions, and control variables of the phase change water heater. The current state variables can be obtained through direct measurement or indirect estimation, and are not limited here. In this embodiment, the current state variables include, but are not limited to, the main temperature points of the phase change water heater and the heat storage capacity of the phase change material.

[0033] When obtaining boundary conditions and control variables, it is necessary to obtain the boundary conditions and control variables over a future period of time. The boundary conditions include, but are not limited to, ambient temperature, and the control variables include, but are not limited to, the heating power of the heater in the phase change water heater.

[0034] Step S102: Obtain the optimization target of the phase change water heater.

[0035] Furthermore, to improve the performance of phase change water heaters, optimization targets need to be determined before optimizing their control. If the goal is to improve the heat charging efficiency, the optimization target can be set to achieve the fastest heat charging efficiency; if the goal is to increase the hot water output, the optimization target can be set to maximize the hot water output. Other optimization targets can also be used in other embodiments.

[0036] Step S103: Based on the current state variables, boundary conditions, control variables and optimization objectives, use the predictive control model to obtain the control decision of the phase change water heater.

[0037] After obtaining the current state variables, boundary conditions, and control variables of the phase change water heater, the state of the phase change water heater in the future (i.e., the prediction window) can be predicted using the predictive control model to obtain the state prediction of the phase change water heater in the future. At this time, the corresponding optimization function and its constraints can be constructed based on the preset optimization objective mentioned above. After obtaining the optimization objective, constructing the corresponding optimization function and its constraints, and the state prediction of the phase change water heater in the future, the optimization solution model in the predictive control model can be used to solve the problem to obtain the control decision of the phase change water heater.

[0038] In this embodiment, the control decision is a series of control variables of the phase change water heater that change over time; that is, the control decision includes multiple sets of control variables of the phase change water heater that change over time.

[0039] Step S104: Control the phase change water heater based on control decisions to achieve the optimization goal.

[0040] After obtaining the control decision of the phase change water heater, the phase change water heater can be controlled over a period of time based on a series of time-varying control variables in the control decision to achieve the optimization goal.

[0041] Unlike existing technologies, the control method for a phase-change water heater in this application includes: acquiring the current state variables, boundary conditions, and control variables of the phase-change water heater; acquiring the optimization objective of the phase-change water heater; using a predictive control model to obtain control decisions for the phase-change water heater based on the current state variables, boundary conditions, control variables, and optimization objective; and controlling the phase-change water heater based on the control decisions to achieve the optimization objective. Through this method, the control method for a phase-change water heater in this application can effectively evaluate the phase-change water heater using a predictive control model, thereby enabling optimized control based on the optimization objective to improve the performance of the phase-change water heater.

[0042] Optionally, a method for obtaining control decisions for a phase change water heater using a predictive control model based on current state variables, boundary conditions, control variables, and optimization objectives is as follows: Figure 2 As shown, please refer to Figure 2 , Figure 2 yes Figure 1 A flowchart illustrating an embodiment of step S103. In this embodiment, the predictive control model includes a predictive model and an optimization solution model, such as... Figure 2 As shown, this embodiment can be achieved through, as... Figure 2 The steps shown in step S103 are specifically steps S201 to S203:

[0043] Step S201: Input the current state variables, boundary conditions, and control variables into the prediction model to obtain the state prediction of the phase change water heater within the prediction window.

[0044] As mentioned above, the predictive control model in this embodiment includes a predictive model and an optimization solution model. After obtaining the current state variables, boundary conditions, and control variables of the phase change water heater, the current state variables, boundary conditions, and control variables for a future period of time can be input into the predictive model. At this time, the predictive model can predict the state of the phase change water heater within the prediction window.

[0045] Step S202: Construct the objective optimization function and its constraints based on the optimization objective.

[0046] After obtaining the optimization objective of the phase change water heater, the objective optimization function and its corresponding constraints can be constructed based on the optimization objective.

[0047] For example, when the optimization objective is to maximize the heat charging rate, the objective function and constraints corresponding to the fastest heat charging rate can be constructed. When the current optimization objective is to maximize the hot water output, the objective function and constraints corresponding to the maximum hot water output can be constructed. The specific construction method is described below and will not be described in detail here.

[0048] Step S203: Based on state prediction, objective optimization function and constraints, use the optimization solution model to obtain the control decision of the phase change water heater.

[0049] After obtaining the state prediction of the phase change water heater for a period of time in the future, the optimization solution model in the predictive control model can be used to solve the problem based on the state prediction, objective optimization function and constraints. The solution of the objective optimization function is then used as the control decision of the phase change water heater within the prediction window.

[0050] Optionally, a method for controlling a phase change water heater based on control decisions, such as... Figure 3 As shown, please refer to Figure 3 , Figure 3 yes Figure 1 A flowchart illustrating an embodiment of step S104. In this embodiment, the control decision includes multiple sets of time-varying control variables within the prediction window, such as... Figure 3 As shown, this embodiment can be achieved through, as follows Figure 3 The steps shown implement step S104, specifically including steps S301 to S302:

[0051] Step S301: Within each prediction window of the phase change water heater, obtain the discrete control variable closest to the current moment from multiple sets of control variables that change over time.

[0052] As mentioned earlier, the control decision includes multiple sets of control variables for the phase change water heater that change over time within the prediction window.

[0053] However, since there may be errors in the prediction model and boundary conditions in the predictive control model mentioned above, when controlling the phase change water heater based on control decisions, the predictive control model needs closed-loop feedback to improve its control accuracy. That is, although the control decision output by the predictive control model each time is a set of control variables of the phase change water heater that change with time within the prediction window, in this embodiment, within each prediction window of the phase change water heater, it is only necessary to obtain the discrete control variable closest to the current time among the multiple sets of control variables that change with time in the control decision within the current prediction window.

[0054] Step S302: Control the phase change water heater to work within the current prediction window based on discrete control variables.

[0055] Within the current prediction window, only the discrete control variable closest to the current time is used to control the phase change water heater, while the remaining control variables are discarded. In the next prediction window, the predictive control model can be solved repeatedly to obtain the discrete control variables in the control decision corresponding to that prediction window to control the phase change water heater.

[0056] Based on the embodiments described above, when the optimization objective changes, the predictive model in the predictive control model described above needs to be adjusted accordingly based on the optimization objective. In this embodiment, when the optimization objective is set to maximize the hot water output, this embodiment needs to construct a corresponding predictive model based on the heat release system of the phase change water heater. Constructing a corresponding predictive model based on the heat release system of the phase change water heater needs to consider the temperature changes of the water and phase change material in the phase change heat heater, the temperature changes of the water in the heater, and the mixing ratio of cold water at the mixing valve.

[0057] Therefore, when the optimization objective is to maximize the hot water output, the prediction model includes a phase change heat exchanger model, a heater model, and a mixing valve model. The phase change heat exchanger model is used to predict the changes in the internal energy of the phase change material and water within the phase change heat exchanger based on the current state variables under the control of boundary conditions and control variables; the heater model is used to predict the changes in the internal energy of the water within the heater based on the current state variables under the control of boundary conditions and control variables; and the mixing valve model is used to simulate the mixing valve under the control of boundary conditions and control variables.

[0058] In this embodiment, the phase change heat exchanger model can be discretized using the finite difference method, with the straight tube and the surrounding phase change material as units. That is, only the water temperature and phase change material temperature distribution along the direction perpendicular to the tube length are considered. The phase change heat exchanger model can be described by the following formula:

[0059]

[0060] In this equation, formula (1) represents the energy conservation of the phase change material element. The left side of formula (1) represents the change in internal energy of the phase change material. The first term on the right side of formula (1) represents the thermal conductivity between the phase change material element and adjacent elements. The second term on the right side of formula (1) represents the heat transfer rate between the phase change material element and the water in the tube. Formula (2) represents the energy conservation of the water element in the tube. The left side of formula (2) represents the change in internal energy of the water. The first term on the right side of formula (2) represents the heat transfer rate between the phase change material element and the water in the tube. The second term on the right side of formula (2) represents the heat transfer rate of the water in adjacent elements due to flow.

[0061] The heater model, considering the lumped parameter method, is described by the following formula:

[0062]

[0063]

[0064] In this equation, formula (3) represents the energy conservation of water inside the heater. The left side of the equation (3) represents the change in the internal energy of water inside the heater. The first term on the right side of the equation (3) represents the electric heating rate. The second term on the right side of the equation (3) represents the heat transfer rate caused by water flow. The third term on the right side of the equation (3) represents the heat dissipation rate of the heater to the environment.

[0065] The mixing valve model is described by the following formula:

[0066]

[0067] Because a single heater is placed at the inlet of the phase change heat exchanger, the outlet water temperature may not reach the set temperature early in the later stages of heat release due to the decay of the phase change material's heat release capacity, which is detrimental to the complete release of stored heat. Therefore, in other embodiments, a first heater can be set at the inlet of the phase change heat exchanger, and a second heater can be set at the outlet of the phase change heat exchanger to improve the release of stored heat. When the phase change water heater is equipped with two heaters, its corresponding prediction model also needs to be set with two heater models, namely a first heater model and a second heater model.

[0068] Similarly, the lumped parameter method can also be considered for the first heater model and the second heater model, as described by the following formula:

[0069]

[0070] In formula (5), the equation represents the energy conservation of water in the first heater. The left side of the equation represents the change in internal energy of water in the first heater. The first term on the right side of the equation represents the electric heating rate. The second term on the equation represents the heat transfer rate caused by water flow. The third term on the equation represents the heat dissipation rate of the heater to the environment. Formula (6) represents the energy conservation of water in the second heater. The left side of the equation represents the change in internal energy of water in the second heater. The first term on the right side of the equation represents the electric heating rate. The second term on the equation represents the heat transfer rate caused by water flow. The third term on the equation represents the heat dissipation rate of the heater to the environment.

[0071] Optionally, when the optimization objective of the phase change water heater is set to maximize the hot water output, the method for constructing the objective optimization function and its constraints based on the optimization objective is as follows: Figure 4 As shown, please refer to Figure 4 , Figure 4 yes Figure 2 A flowchart illustrating step S202 of the first embodiment. (See attached diagram.) Figure 4 As shown, this embodiment can be achieved through, as follows Figure 4 The steps shown in step S202 are implemented by steps S401 to S402:

[0072] Step S401: Obtain the first equivalent constraint condition corresponding to the maximum hot water volume.

[0073] Based on the predictive model constructed from the heat release system of the phase change water heater described above, the control objective in this implementation is to release the maximum amount of hot water while meeting the outlet water temperature of the phase change water heater.

[0074] However, it is not convenient to construct the objective function for maximizing the hot water output. Therefore, it is necessary to obtain the first equivalent constraint condition corresponding to maximizing the hot water output.

[0075] Optionally, the first equivalent constraint includes minimizing the reduction rate of the liquid proportion of the phase change material or maximizing the power consumption of the heater in the phase change water heater.

[0076] In this embodiment, the first equivalent constraint can be that the heater consumes the maximum amount of electricity. This is because, according to the law of conservation of energy, the heat released by the phase change water heater comes from the sum of the heat stored in the phase change material of the phase change heat exchanger and the heat generated by the heater. Since the heat stored in the phase change material is a constant, releasing the maximum amount of hot water can be equivalent to maximizing the power consumption of the heater in the future.

[0077] In other embodiments, the first equivalent constraint can also be that the reduction rate of the liquid content of the phase change material is minimized.

[0078] Step S402: Construct the first objective optimization function and its first constraint conditions based on the first equivalent constraint conditions, the physical model of the phase change water heater, the constraints of the state variables, the constraints of the control variables, and the heat release constraints.

[0079] After obtaining the first equivalent constraint condition that maximizes the hot water output, the first objective optimization function and its first constraint condition can be constructed based on the first equivalent constraint condition, the physical model of the phase change water heater, the constraints of state variables, the constraints of control variables, and the heat release constraint.

[0080] Furthermore, for the same objective of maximizing the output of hot water, there may be multiple equivalent constraints, and the corresponding first objective optimization function and its first constraint may also be written in different ways, but they can all achieve the same optimization objective. Although the difficulty of solving different ways may differ, the basic principle is the same, and no restrictions will be imposed here.

[0081] When the first equivalent constraint is that the heater consumes the maximum amount of electricity, and the phase change heater has only one heater, its first objective function and its first constraint are shown in the following formula:

[0082] min∑ t -P heater,t (7)

[0083] stx t+Δt=A·x t +B·u t (8)

[0084]

[0085] x t ∈[x min ,x max (10)

[0086] u t ∈[u min ,u max (11)

[0087] Among them, formula (7) is the first objective optimization function, and formulas (8)-(11) are the first constraints; formula (8) is the vector linearization representation of the physical model of the phase change water heater, which constrains the change of state variables to not override physical laws; formula (9) is the constraint of the outlet water temperature, which restricts the opening of the mixing valve (assuming that the mixing flow rate and the opening are monotonic); formula (10) is the constraint of the state variables, such as the heater outlet water temperature not exceeding the threshold; formula (11) is the constraint of the control variables, such as the opening of the mixing valve / the electric power of the heater not exceeding the adjustable range.

[0088] In other embodiments, when the first equivalent constraint is that the heater consumes the most electricity and the phase change heater has two heaters, the first objective optimization function is as shown in formula (12):

[0089] min∑ t -(P heater1,t +P heater2 (12)

[0090] The first constraint condition of formula (12) is the same as the first constraint condition of formula (7).

[0091] When the first equivalent constraint is to minimize the reduction rate of the liquid content of the phase change material, its first objective function and its first constraint are shown in the following formula:

[0092]

[0093] stx t+Δt =A·x t +B·u t (14)

[0094]

[0095] x t ∈[x min ,x max (16)

[0096] u t ∈[u min ,u max (17)

[0097]

[0098] Among them, formulas (14)-(17) are the same as formulas (8)-(11) above, and will not be repeated. In formula (13), α is the weight. When t is relatively small, α should be relatively large to avoid the underoptimization situation of the rate being large first and then small in the prediction window when it is close to exothermic. Therefore, in this case, a constraint condition needs to be added, namely formula (18), to ensure that the process is an exothermic process.

[0099] In existing technologies, the control logic of current phase change water heaters is as follows: The system flow rate and the phase change heat exchanger outlet temperature are measured. If the system flow rate is greater than a certain threshold (indicating the water heater is discharging hot water) and the phase change heat exchanger outlet temperature is lower than the phase change temperature of the phase change material, then the phase change heat exchanger requires auxiliary heating. Under this condition, the difference between the phase change temperature and the phase change heat exchanger outlet temperature is calculated. When the temperature difference is small, the electric heater outputs low power; conversely, when the temperature difference is large, the electric heater outputs high power. This control is relatively simple, but it cannot maximize the amount of hot water produced.

[0100] Unlike existing technologies, in this embodiment, when the optimization objective is set to maximize the hot water output, the predictive control model of this embodiment can quantitatively estimate the heat storage state of the phase change heat exchanger. By solving the first objective optimization function, the optimal electrothermal power of the heater, the heat release rate of the phase change material, and the relationship between the cold water mixing volume can be obtained, thereby optimizing the heat release process and maximizing the hot water output while ensuring that the outlet water temperature meets the requirements.

[0101] As mentioned earlier, when the optimization objective changes, the predictive model in the predictive control model needs to be adjusted accordingly. In this embodiment, when the optimization objective is set to the fastest heat charging efficiency, a corresponding predictive model needs to be constructed based on the heat charging system of the phase change water heater. Constructing a corresponding predictive model based on the heat charging system of the phase change water heater only requires considering the dynamic temperature changes of the water in the phase change heat heater and the phase change material (i.e., the water in the heater).

[0102] Therefore, when the optimization objective of the phase change water heater is set to maximize the hot water output, the predictive model in its predictive control model includes a phase change heat exchanger model and a heater model. The phase change water heater model is used to predict the internal energy changes of the phase change material and water in the phase change heat exchanger based on the current state variables under the control of boundary conditions and control variables. The heater model is used to predict the internal energy changes of the water in the heater based on the current state variables under the control of boundary conditions and control variables.

[0103] In this embodiment, the phase change heat exchanger model can be discretized using the finite difference method, with the straight pipe and the surrounding phase change material as units, that is, only the water temperature and phase change material temperature distribution along the vertical direction of the pipe length are considered. The phase change heat exchanger model can be described by formulas (1) and (2) mentioned above. The heater model considers the lumped parameter method and can be described by formula (3) mentioned above. Similarly, if the phase change water heater in this embodiment is also equipped with two heaters, two heater models can also be set in the prediction model. These two heater models can also be described by formulas (5) and (6) mentioned above.

[0104] Optionally, when the optimization objective of the phase change water heater is set to maximize the heat charging efficiency, the method for constructing the objective optimization function and its constraints based on the optimization objective is as follows: Figure 5 As shown, please refer to Figure 5 , Figure 5 yes Figure 2 A flowchart illustrating step S202 of the second embodiment. (See attached diagram.) Figure 5 As shown, this embodiment can be achieved through, as follows Figure 5 The steps shown in step S202 are implemented by steps S501 to S502:

[0105] Step S501: Obtain the second equivalent constraint condition corresponding to the fastest heat charging efficiency.

[0106] Based on the predictive model constructed from the heat charging system of the phase change water heater described above, the control objective in this implementation is to achieve the fastest possible heat charging rate for the phase change water heater while ensuring that the system does not overheat.

[0107] However, it is not convenient to construct the objective function for achieving the fastest heat charging efficiency. Therefore, it is necessary to obtain the second equivalent constraint condition corresponding to the fastest heat charging efficiency.

[0108] Optionally, the second equivalent constraint includes the largest increase in the liquid proportion of the phase change material or the largest power consumption of the heater in the phase change water heater.

[0109] In this embodiment, the second equivalent constraint can be that the heater consumes the most electricity, because according to the law of conservation of energy, all the heat during charging comes from the heater. Therefore, the fastest charging efficiency can be equivalent to the heater consuming the most electricity in the future.

[0110] In other embodiments, the second equivalent constraint can also be that the liquid content of the phase change material increases at the maximum rate.

[0111] Step S502: Construct the second objective optimization function and its second constraint conditions based on the second equivalent constraint conditions, the physical model of the phase change water heater, the constraints of the state variables, the constraints of the control variables, and the heat charging constraints.

[0112] After obtaining the second equivalent constraint that yields the fastest heat charging efficiency, the second objective optimization function and its second constraint can be constructed based on the second equivalent constraint, the physical model of the phase change water heater, the constraints of state variables, the constraints of control variables, and the heat charging constraint.

[0113] Furthermore, for the same objective of maximizing heat output efficiency, there are multiple equivalent second constraints, and the corresponding second objective optimization functions and second constraints can also be written in different ways. However, they can all achieve the same optimization objective. Although the difficulty of solving different ways varies, the basic principle is the same, and no restrictions are imposed here.

[0114] When the second equivalent constraint is that the heater power consumption is maximized and there is only one phase change heater, its first objective function and its first constraint are as follows:

[0115] min∑ t -P heater,t (19)

[0116] stx t+Δt =A·x t +B·u t (20)

[0117] x t ∈[x min ,x max ](twenty one)

[0118] u t ∈[u min ,u max ](twenty two)

[0119] Among them, formula (19) is the second objective optimization function, and formulas (20)-(22) are the second constraints; formula (20) is the vector linearization representation of the physical model of the phase change water heater (i.e., all differential equations in the predictive model in the predictive control model), which constrains the change of state variables to not override physical laws; formula (21) is the constraint of state variables, such as the outlet water temperature of the heater not exceeding the threshold; formula (22) is the constraint of control variables, such as the flow rate of the water pump / the electric power of the heater not exceeding the adjustable range.

[0120] In other embodiments, when the second equivalent constraint is that the heater power consumption is maximum and the phase change heater has two heaters, the second objective optimization function is as shown in formula (23):

[0121] min∑ t -(P heater1,t +P heater2 )(twenty three)

[0122] The second constraint condition of formula (23) is the same as the second constraint condition of formula (19).

[0123] When the second equivalent constraint is that the liquid proportion of the phase change material increases at its maximum rate, the second objective function and its second constraint are shown in the following formula:

[0124]

[0125] stx t+Δt =A·x t +B·u t (25)

[0126] x t ∈[x min ,x max (26)

[0127] u t ∈[u min ,u max (27)

[0128]

[0129] Among them, formulas (25)-(27) are the same as formulas (20)-(22) above, and will not be repeated. In formula (28), α is the weight. When t is relatively small, α should be relatively large to avoid the underoptimization situation of the rate being large first and then small in the prediction window when it is close to the heat release. Therefore, in this case, a constraint condition needs to be added, namely formula (28), to ensure that the process is a heat charging process.

[0130] In existing technologies, the control logic of current phase change water heaters is as follows: The system flow rate and the inlet and outlet temperatures of the phase change heat exchanger are measured. If the system flow rate is less than a certain threshold (indicating the water heater is not in use) and the outlet temperature of the phase change heat exchanger is lower than both the set temperature and the phase change temperature of the phase change material, then the phase change heat exchanger needs to be charged. Under this condition, the temperature difference between the inlet and outlet of the phase change heat exchanger is calculated. When the temperature difference is small, the water pump outputs a large flow rate while the electric heater outputs a small power; conversely, when the temperature difference is large, the water pump outputs a small flow rate while the electric heater outputs a large power. This control is relatively simple but cannot maximize the charging efficiency.

[0131] Unlike existing technologies, in this embodiment, when the optimization objective is set to the fastest heat charging efficiency, the predictive control model of this embodiment can quantitatively estimate the heat storage state of the phase change heat exchanger. By solving the second objective optimization function, the optimal relationship between the heating power and the heat absorption rate of the phase change material over a period of time can be obtained, thereby optimizing the heat charging process and making the heat charging rate reach the fastest.

[0132] The meanings of the English letters, Greek letters and subscripts in formulas (1) to (28) in the previous embodiments are detailed in the table below.

[0133]

[0134]

[0135] Optionally, this application further proposes a phase change water heater system; please refer to [link to relevant documentation]. Figure 6 , Figure 6 This is a schematic diagram of the structure of the first embodiment of the phase change water heater system of this application. Figure 6 As shown, the phase change water heater system 100 of this embodiment includes a phase change water heater 10 and a controller 20, wherein the controller 20 is connected to the phase change water heater 10 and is used to control the phase change water heater 10 based on any of the control methods of the phase change water heater 10 described above.

[0136] Optionally, such as Figure 6 As shown, the phase change water heater 10 includes a first heater 11, a phase change heat exchanger 12, a water pump 13, and a mixing valve 14. The inlet of the first heater 11 is connected to the water inlet, the outlet of the first heater 11 is connected to the inlet of the phase change heat exchanger 12, the outlet of the phase change heat exchanger 12 is connected to the water pump 13, the water pump 13 is connected to the first end of the mixing valve 14, and the second and third ends of the mixing valve 14 are also connected to the water inlet and the water outlet, respectively.

[0137] Alternatively, in other embodiments, please refer to Figure 7 , Figure 7 This is a schematic diagram of the structure of the second embodiment of the phase change water heater system of this application. Figure 7 As shown, the phase change water heater system 100 of this embodiment includes a phase change water heater 10 and a controller 20. The phase change water heater 10 includes a phase change heat exchanger 12, a first heater 11, a second heater 15, a water pump 13, and a mixing valve 14. The inlet of the first heater 11 is connected to the water inlet, the outlet of the first heater 11 is connected to the inlet of the phase change heat exchanger 12, the outlet of the phase change heat exchanger 12 is connected to the inlet of the second heater 15, the outlet of the second heater 15 is connected to the water pump 13, the water pump 13 is connected to the first end of the mixing valve 14, and the second and third ends of the mixing valve 14 are also connected to the water inlet and the water outlet, respectively.

[0138] Based on the above Figure 6 and Figure 7 In this embodiment, the phase change heat exchanger 12 has a finned heat exchanger structure inside, and the finned side is filled with phase change material; the power of the first heater 11 and the second heater 15 is set to be multi-stage or continuously adjustable.

[0139] The mixing valve 14 is set as an electric mixing valve. Compared with the manual mixing valve and thermostatic valve of the prior art, in this embodiment, the mixing valve 14 is set as an electric mixing valve and is used in conjunction with the predictive control model of this application, which can make the phase change water heater 10 adjust the temperature faster and the outlet water temperature more stable.

[0140] Optionally, this application further proposes a readable storage medium. See also... Figure 8 , Figure 8 This is a schematic diagram of the structure of an embodiment of the readable storage medium of this application.

[0141] The readable storage medium 200 of this application embodiment stores program instructions 210, which are executed by a processor to implement the control method of the phase change water heater in any of the above embodiments.

[0142] Specifically, program instructions 210 can form a program file and be stored in the aforementioned storage medium as a software product, so that an electronic device (which may be a personal computer, server, or network device, etc.) or processor can execute all or part of the steps of the methods of the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks, or terminal devices such as computers, servers, mobile phones, and tablets.

[0143] In this embodiment, the readable storage medium 200 may be, but is not limited to, a USB flash drive, SD card, PD optical drive, portable hard drive, large-capacity floppy drive, flash memory, multimedia memory card, server, etc.

[0144] In one embodiment, a computer program product or computer program is provided, comprising computer instructions stored in a readable storage medium. A processor of an electronic device reads the computer instructions from the readable storage medium and executes the computer instructions, causing the electronic device to perform the steps described in the above method embodiments.

[0145] Furthermore, if the aforementioned functions are implemented as software functions and sold or used as independent products, they can be stored in a mobile terminal-readable storage medium. That is, this application also provides a storage device storing program data, which can be executed to implement the methods of the above embodiments. This storage device can be, for example, a USB flash drive, an optical disc, or a server. In other words, this application can be embodied in the form of a software product, which includes several instructions to cause a smart terminal to execute all or part of the steps of the methods described in the various embodiments.

[0146] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0147] Any process or method description in the flowchart or otherwise herein can be understood as representing an apparatus, segment, or portion of code comprising one or more executable instructions for implementing a particular logical function or process, and the scope of the preferred embodiments of this application includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order according to the functions involved, as should be understood by those skilled in the art to which embodiments of this application pertain.

[0148] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (which may be a personal computer, server, network device, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable media include: an electrical connection having one or more wires (electronic device), a portable computer disk drive (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Alternatively, the computer-readable medium may be paper or other suitable media on which the program can be printed, since the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in a computer memory.

[0149] The above description is merely an embodiment of this application and does not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A control method for a phase change water heater, characterized in that, include: Obtain the current state variables, boundary conditions, and control variables of the phase change water heater; Obtain the optimization target of the phase change water heater; Based on the current state variables, the boundary conditions, the control variables, and the optimization objective, the control decision of the phase change water heater is obtained using a predictive control model. The phase change water heater is controlled based on the control decision to achieve the optimization objective.

2. The control method according to claim 1, characterized in that, The predictive control model includes a predictive model and an optimization solution model. The step of obtaining the control decision of the phase change water heater using the predictive control model based on the current state variable, the boundary conditions, the control variable, and the optimization objective includes: The current state variable, the boundary conditions, and the control variable are input into the prediction model to obtain the state prediction of the phase change water heater within the prediction window; Construct the objective optimization function and its constraints based on the aforementioned optimization objective; Based on the state prediction, the objective optimization function, and the constraints, the optimization solution model is used to obtain the control decision of the phase change water heater.

3. The control method according to claim 2, characterized in that, The optimization objective includes maximizing the hot water output. The step of constructing the objective optimization function and its constraints based on the optimization objective includes: Obtain the first equivalent constraint condition corresponding to the maximum hot water output; Based on the first equivalent constraint, the physical model of the phase change water heater, the constraints of the state variables, the constraints of the control variables, and the heat release constraint, a first objective optimization function and its first constraint are constructed.

4. The control method according to claim 3, characterized in that, The first equivalent constraint condition includes the minimum reduction rate of the liquid content of the phase change material or the maximum power consumption of the heater of the phase change water heater.

5. The control method according to claim 3, characterized in that, The prediction model includes a phase change heat exchanger model, a heater model, and a mixing valve model; The phase change water heater model is used to predict the internal energy changes of the phase change material and water in the phase change water heater based on the current state variables under the control of the boundary conditions and the control variables; the heater model is used to predict the internal energy changes of the water in the heater based on the current state variables under the control of the boundary conditions and the control variables; the mixing valve model is used to simulate the mixing valve under the control of the boundary conditions and the control variables.

6. The control method according to claim 2, characterized in that, The optimization objective includes maximizing heat charging efficiency. The step of constructing the objective optimization function and its constraints based on the optimization objective includes: Obtain the second equivalent constraint condition corresponding to the fastest heat charging efficiency; Based on the second equivalent constraint, the physical model of the phase change water heater, the constraints of state variables, the constraints of control variables, and the heat charging constraint, a second objective optimization function and its second constraint are constructed.

7. The control method according to claim 6, characterized in that, The second equivalent constraint condition includes either the maximum growth rate of the liquid proportion of the phase change material or the maximum power consumption of the heater of the phase change water heater.

8. The control method according to claim 6, characterized in that, The prediction model includes a phase change heat exchanger model and a heater model; The phase change water heater model is used to predict the internal energy changes of the phase change material and water in the phase change water heater based on the current state variables under the control of the boundary conditions and the control variables; the heater model is used to predict the internal energy changes of the water in the heater based on the current state variables under the control of the boundary conditions and the control variables.

9. The control method according to claim 1, characterized in that, The control decision includes multiple sets of time-varying control variables within a prediction window, and the step of controlling the phase change water heater based on the control decision includes: Within each prediction window of the phase change water heater, the discrete control variable closest to the current moment is obtained from multiple sets of control variables that change over time; The phase change water heater is controlled to operate within the current prediction window based on the discrete control variables.

10. A phase change water heater system, characterized in that, The invention includes a phase change water heater and a controller, wherein the controller is connected to the phase change water heater and is used to control the phase change water heater based on the control method of any one of claims 1-9.

11. The phase change water heater system according to claim 10, characterized in that, The phase change water heater includes a phase change heat exchanger, a first heater, a water pump, and a mixing valve. The inlet of the first heater is connected to the water inlet, the outlet of the first heater is connected to the inlet of the phase change heat exchanger, the outlet of the phase change heat exchanger is connected to the water pump, the water pump is connected to the first end of the mixing valve, and the second and third ends of the mixing valve are respectively connected to the water inlet and the water outlet.

12. The phase change water heater system according to claim 11, characterized in that, The phase change water heater also includes a second heater, the outlet of the phase change water heater is connected to the inlet of the second heater, and the outlet of the second heater is connected to the water pump.

13. A readable storage medium, characterized in that, It internally stores program instructions, which are executed to implement the control method for the phase change water heater according to any one of claims 1-9.

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